1. Field of the Invention
The present invention relates to the field of disk drives and peripheral components for a computer system. More particularly, the present invention relates to a system and method for controlling power of a disk drive or of a peripheral component for a computer system.
2. Description of the Related Art
Hard Disk Drives (HDDs) have multiple power modes that trade-off energy consumption for response time. Accordingly, a relatively short response time has an associated relatively higher energy consumption because a greater proportion of the HDD is powered up and active. Typical power modes for an HDD include Active, Idle, Standby and Sleep modes. Other mobile computer peripheral devices, such as a microprocessor (xcexcP) and a liquid crystal display (LCD), provide power modes that are analogous to HDD power modes.
An HDD operating in the Sleep mode, which consumes the least amount of power of the different power modes, returns to the Active mode in response to a specific command received by the HDD. An HDD operating in either of the Idle and Standby modes returns to the Active mode in response to any command received by the HDD, so that the use of the low-power Idle and Standby modes are transparent to the host system. Such capability requires that the interface remain responsive and that state information is retained by the HDD during the Idle and Standby modes. These functions are achieved by keeping the interface control electronics of the HDD fully operational during both the Idle and Standby modes.
For example, when an HDD is operating in the Standby mode, bus commands are constantly monitored and interpreted. To do this, the hard disk controller (HDC), the microprocessor (xcexcP), the random access memory (RAM) and the clocking (CLK) circuits of the HDD must each be operational. The corresponding power consumption is about 300 mW, and the recovery time from the Standby mode is about 1.5 seconds.
Low-power modes for HDDs are characterized by reducing or halting electronic functions and slowing or halting mechanical motion. For example, in the Standby mode for an HDD, the disk is not spinning, and much of the electronics are powered down. The interface electronics, however, remain powered, typically consuming 250 mW. Because the interface activity is minimal during a low-power mode, much of the power used for the interface is wasted.
What is needed is a way to control the interface power consumption of a device so that the device power consumption is substantially reduced from that in conventional low-power modes of the device.
The present invention provides a system and method for controlling the power consumption in a device so that the device power consumption is substantially reduced in comparison to conventional low-power modes of the device, and so that there is minimal impact on performance and no need for host intervention. In particular, power consumption may be substantially reduced from that of a device operating in a conventional Standby power mode.
The advantages of the present invention are provided by a device, such as an HDD, that includes operational logic and power control logic. The operational logic is responsive to communication signals over an interface from a host for performing I/O operations. The operational logic also provides a first and a second mode of operation, such that the second mode of operation consumes less power than the first mode of operation. In the first mode of operation, the device is coupled to the interface and is ready to respond to I/O communications. Preferably, the first mode of operation is an Active, Idle or Standby mode of operation. The second mode of operation is an enhanced low power mode. The power control logic is coupled to the communication signals from the interface and controls the operational logic when the operational logic is in the second mode of operation. The power control logic enables the operational logic to enter the first mode of operation when the power control logic detects a communication signal over the interface, such as a Write command, that requires the operational logic to be in the first mode of operation.
According to the invention, the power control logic includes monitor logic, a command register and a state value memory. The monitor logic is connected to an interface, such as an ATA bus. The monitor logic generates a control signal in response to the predetermined communication signal over the interface. The command register stores the predetermined communication signal in response to the control signal, and the state value memory stores state values for the first mode of operation of the operational logic when the operational logic is in the second mode of operation. The power control logic also includes a status register that stores status information of the operational logic when the operational logic is in the second mode of operation. When the monitor logic detects a status read communication signal, a read signal is generated. The status register then outputs the status information in response to the read signal.